During a nitration process to produce a desired chemical product, such as nitrotoluene or nitrobenzene, nitrophenolic by-products are produced. These by-products are separated from the desired nitrated product by washing. The by-products are then present in the wash water or waste water stream which must be disposed of without harming the environment.
There are various processes known in the art for disposing of waste water containing nitrophenolic materials. The nitrophenolic materials are usually present in the form of di- and tri-nitrophenols and di- and tri-nitrocresols. One current process for disposing of these by-products is to collect the waste water from the nitration washers in a lagoon and adjust the pH of the waste water to approximately 1.5 causing as much of the phenolic compounds as possible to precipitate. However, due to environmental concerns and the increasing number of chemical by-products which must be disposed of safely, alternative methods must be utilized.
Numerous processes are disclosed in the art for separating out nitrophenolic materials from waste water allowing for the disposal of the waste water in a conventional manner. For example, U.S. Pat. No. 4,469,561 discloses the recovery of bisphenol A and phenol from aqueous effluent streams using toluene as a solvent in a liquid-liquid extraction. Specifically, bisphenol A, phenol, and toluene are passed through an extraction column. The resulting aqueous phase, which is a toluene solution of bisphenol A and phenol, is removed and treated so that the individual components of bisphenol A, phenol, and toluene are recovered from the aqueous solution. The toluene is recycled to the extraction column for further use.
U.S. Pat. No. 4,597,875 discloses the production of dinitrotoluene with the concurrent production of nitrophenolic by-products, i.e. nitrocresols and picric acid. Prior to disposal of the waste water, the by-products are removed from the waste water. The waste water is first contacted with an alkaline material to convert the by-products to water soluble salts. An organic and aqueous phase are generated. The aqueous phase, which contains the nitrophenolic materials, is separated out and treated with an acid to convert the salts to a water insoluble material. The water-insoluble material separates into an organic phase containing the converted nitrophenolic materials and an aqueous phase containing water soluble salts. The organic phase, due to its low water content, can then be incinerated to dispose of the contaminants.
U.S. Pat. Nos. 2,808,375 and 2,812,305 disclose the purification of phenol contaminated waste waters utilizing a specified compound in combination with a solvent. The '375 and '305 patents disclose that it is known to extract undesirable phenols from waste water utilizing a solvent such as toluene. However, it is also disclosed that conventional extraction methods require five stages of extraction to remove all but a trace amount of the phenols. The '375 patent discloses the use of dehydroabietylamine and a solvent, such as toluene, in a three stage extraction process to remove the phenols from the waste water. The '305 patent discloses the use of 2-methyl-5-ethylpyridine in combination with a solvent, such as toluene, in a three stage extraction process to remove the phenols from the waste water.
U.S. Pat. No. 2,199,786 discloses the extraction of phenols from an aqueous solution utilizing liquid esters of carboxylic acid. Optionally, an additional solvent, such as toluene can be utilized with the ester.
U.S. Pat. No. 3,467,721 discloses the separation of phenols from an aqueous mixture utilizing mesityl oxide. Optionally, a second solvent, such as toluene, can be used in combination with the oxide.
U.S. Pat. Nos. 4,152,528 and 4,160,111 disclose the extraction of phenols from an aqueous mixture utilizing a combination of a ketone and a hydrocarbon compound, such as toluene, as the extracting medium.
U.S. Pat. No. 2,675,412 discloses the recovery of solvents from waste gases resulting from extraction processes. Phenol-containing waters are subjected to an extraction process. A separator then separates the water phase and the solvent containing phase. The solvent containing phase is then subjected to distillation to recover the solvent for further use. The phenols are subjected to any desired further treatment. The '412 patent does not specify the further treatment of the phenols.
U.S. Pat. No. 2,807,654 discloses the removal of phenols from waste water utilizing a solvent, such as an aromatic hydrocarbon, and a salt.
U.S. Pat. No. 4,421,649 discloses the removal of chlorinated hydrocarbon solid particles from an aqueous suspension. The suspension is acidified prior to extraction. Extraction utilizing a solvent then takes place whereby the solvent takes up the sludge from the suspension. A preferred solvent is disclosed as an aromatic petroleum fraction, such as kerosene.
The art does not disclose the treatment of nitrophenolic by-products utilizing an extraction process including the concurrent use of a solvent with an acid as described in the present invention. The extraction of nitrophenolic by-products of the present invention is both efficient and economical. The present invention additionally provides for the recovery of the solvent while placing the nitrophenolic by-products in a form suitable for environmentally safe disposal.